dav: add default implementation for save_resource

crates/caldav/src/calendar_object/resource.rs

@@ -185,10 +185,6 @@ impl<C: CalendarStore + ?Sized> ResourceService for CalendarObjectResourceServic
         })
     }
 
-    async fn save_resource(&self, _file: Self::Resource) -> Result<(), Self::Error> {
-        Err(Error::NotImplemented)
-    }
-
     async fn delete_resource(&self, use_trashbin: bool) -> Result<(), Self::Error> {
         self.cal_store
             .delete_object(&self.principal, &self.cal_id, &self.object_id, use_trashbin)